Whatever the outcome of the Nov. 2 elections, you can be certain that commentators around the country will be fixated on the impact of the Tea Party movement. If Republican candidates do well on Election Day –- and particularly if Tea Party-backed candidates like Rand Paul of Kentucky and Sharron Angle of Nevada win their races -– the Tea Party will be credited with having revived a moribund Republican Party. But if the Republicans fail to live up to expectations — and expectations are exceedingly high –- the Tea Party will be blamed for curbing the Republicans’ ability to capitalize on historic levels of voter dissatisfaction.

These headlines are unlikely to do justice, however, to a complex movement that is hard enough to define, let alone to evaluate.

At the nucleus of the Tea Party is disquiet over the direction of the country, and antipathy toward what is seen to be profligate levels of spending and governmental involvement in the economy. The Tea Party, however, has little formal organizational infrastructure. Some groups -– like FreedomWorks, the Tea Party Express, and the Tea Party Patriots –- claim to speak for it, as do some individuals like Glenn Beck and Jim DeMint. But they do not always agree on things as basic as which candidates to endorse. FreedomWorks, for instance, declined to endorse Christine O’Donnell in Delaware, fearing she was unelectable, while many of the other groups did.

Nor does the Tea Party have any official platform. And there seems to be little interest among members of the Tea Party at forming a political party proper; instead, most of its stakeholders are seeking to reinvent the Republican Party’s brand.

Any effort to assess the impact of Tea Party needs to keep this context in mind. Moreover, there are several distinct dimensions along which the Tea Party might be evaluated -– and they lead to some relatively complex conclusions about its effects.

Dimension 1: Tea Party’s impact on specific races

This first dimension -– how a Tea Party candidate has affected Republican chances of winning a particular Congressional or gubernatorial seat — has probably been the most widely examined, perhaps because it is relatively tangible. We can evaluate, for instance, the impact of Tea Party candidates on specific United States Senate races.

There are 10 Republicans who have made it into the November ballot for the Senate this year that enjoy the endorsements of most (although not necessarily all) Tea Party affiliated groups: Sharron Angle of Nevada; Ken Buck of Colorado; Jim DeMint of South Carolina; Ron Johnson of Wisconsin; Mike Lee of Utah; Joe Miller of Alaska; Christine O’Donnell of Delaware; Rand Paul of Kentucky; Marco Rubio of Florida; and Pat Toomey of Pennsylvania.

In two cases, the selection of a Tea Party-backed candidate has come at the direct expense of another candidate who appeared to be more electable:

In Delaware, Republicans have come as close as possible to giving away a Senate seat. Ms. O’Donnell is now almost a 95 percent underdog in her race, according to the FiveThirtyEight forecast model, whereas her opponent in the Republican primary, Mike Castle, would have been a 95 percent favorite, according to the same formula. In Nevada, Ms. Angle now has about even odds of prevailing in her race against Harry Reid. What is less clear is how either of the so-called establishment alternatives -– Sue Lowden and Danny Tarkanian -– might have done. Ms. Lowden, for instance, once held leads of as many as 15 points over Mr. Reid in the polls. But, after a number of miscues by Ms. Lowden, Mr. Reid had closed his deficit and drawn the race closer to even by the time of the primaries in Nevada on June 8. My working assumption is that Ms. Lowden or Mr. Tarkanian would probably have been about 70 percent favorites to defeat Mr. Reid -– but there is some guesswork involved here.

In two states, a Tea Party candidate may have harmed the Republicans by triggering an establishment Republican to defect from the party and run as an independent.

In Florida, Gov. Charlie Crist, who is running as an independent, has seen his numbers fade, and the Tea Party backed Mr. Rubio is now about an 80 percent favorite to win his race against Mr. Crist and the Democrat, Kendrick B. Meek. But had Mr. Crist been matched up directly against Mr. Meek, he would probably have been favored by a still-larger magnitude; polls had him about 14 points ahead of Mr. Meek at the time he exited the Republican primary under pressure from Mr. Rubio. In Alaska, Joe Miller’s primary victory has triggered a write-in bid by Senator Lisa Murkowski, whom he defeated. Ms. Murkowski’s chances are not easy to assess, but the political futures market Intrade now gives Mr. Miller about a 60 percent chance of holding the seat for Republicans. Although I think Intrade’s assessment of Mr. Miller’s chances is too pessimistic, this nevertheless reflects a downgrade for Republicans, who would have been almost certain to win the seat had Ms. Murkowski been in a one-on-one matchup against the Democrat, Scott McAdams.

One case is hopelessly ambiguous:

Mr. Toomey of Pennsylvania, who entered the Republican primary as a conservative alternative to Arlen Specter, probably forced Mr. Specter to defect to the Democratic Party, where he cast a number of important votes on behalf of the Democrats. Mr. Toomey is now a clear favorite against the Democrat in the race, Joe Sestak, who defeated Mr. Specter in the Democratic primary. What sort of chances the Democrats would have had if Mr. Specter had remained in the Republican Party and had been the nominee is unclear.

There is one case in which the Tea Party candidate seems to have improved Republican chances:

In Wisconsin, the businessman Ron Johnson, who seems to have found his inspiration to run for office from the Tea Party, has made the race against Senator Russ Feingold competitive; indeed, Mr. Johnson led the most recent Rasmussen Reports poll there by 7 points. Although I’d urge caution on characterizing the race, which has been inadequately polled, he seems to have placed the Republicans in a stronger position than his opponent in the Republican primary, Dave Westlake, who had trailed Mr. Feingold in all polls.

In the other four states, the Tea Party candidate has had little obvious impact. Mr. Lee of Utah upended a Republican incumbent, Senator Robert Bennett. But Mr. Lee is almost certain to defeat the Democrat, Sam Granato, as Mr. Bennett would have been. Mr. DeMint of South Carolina, an incumbent, was under no real threat of losing either the primary or the general election. Mr. Paul of Kentucky, and Mr. Buck of Colorado, were not doing obviously better or worse in general election polling than the establishment alternatives at the time they won their primaries, and both are now favored to win their races.

Other than in Delaware, then, the immediate impact of Tea Party candidates upon electoral outcomes is therefore somewhat more ambiguous than you might think (although it has probably been harmful to the Republicans on balance). Delaware, however, counts for a lot, having significantly reduced Republican chances of taking over the Senate. Whereas early in the political cycle, the Tea Party had largely avoided directly undermining the potential for Republican electoral gains, it elected Ms. O’Donnell in the face of clear warnings from the Republican establishment.

Dimension 2: Tea Party’s impact on voter enthusiasm

The contours of this election are unusual. While the Democratic Congress has become very unpopular, and the Democratic president somewhat so, views of the Republican Party remain highly negative, and have not improved appreciably from the damaged condition following George W. Bush’s two terms as president. And yet, Republicans appear poised for large electoral gains.

One reason may be, as I have argued several times, that the Tea Party has provided a vehicle by which fiscal conservatism, which has never gone out of style, has been liberated from the Republican brand. In addition, the Tea Party has probably contributed toward higher levels of enthusiasm among conservative-leaning voters. And it may have played a key role in souring public opinion on Democratic initiatives like health care and the stimulus.

One possible course for these midterms was a low-turnout election, with voter apathy toward both major parties. The Democrats might still have lost quite a few seats in Congress –- simply because they were the incumbent party and had more of them to lose — but the losses would probably not have been catastrophic. The Tea Party, however, has made some conservatives feel as though they have a real alternative -– something new and fresh and different — to Democratic governance. The impact of this is hard to evaluate, but it could easily outweigh the loss of a Senate seat or two in specific cases like Delaware.



Dimension 3: Tea Party and perceptions of Republican “extremism”

After several victories by Tea Party candidates, like Mr. Paul’s in Kentucky and Ms. Angle’s in Nevada, there has been something of a feeding frenzy on liberal blogs (and to some extent, political media outlets in general), which have sought to unearth whatever uncouth statements, or unorthodox policy positions, the candidate has in his or her background. This process is still underway with Ms. O’Donnell in Delaware. What liberals seem to be banking on is that candidates like these will pollute the Republican brand by being poor standard-bearers. Indeed, the White House is considering formalizing the strategy, according to reporting by The Times.

Although the risks are perhaps greater to Republicans with Ms. O’Donnell than with the previous candidates, so far it is unclear that the strategy has worked. Mr. Paul, for instance, has seen his standing improve in Kentucky since his primary win there in May, and meanwhile, the Republicans have somewhat strengthened their position nationally.

One problem may be that, if the Tea Party appears extreme to some voters, the Democratic agenda does to others. Arguably, in fact, the Tea Party — by normalizing extremely conservative viewpoints — makes mainstream Democratic views seem more extreme by comparison.

Also, many Republican candidates are not of the Tea Party. What does pointing toward the extremism of Ms. O’Donnell, or Ms. Angle, do to perceptions of a boring ol’ establishment Republican candidate like Rob Portman of Ohio? In some ways, does it not represent an implicit endorsement of Mr. Portman for “not being one of the crazy ones”? It is not clear how much good this type of messaging will do for Democratic candidates outside the borders of Delaware, or Kentucky, or Nevada.

Dimension 4: Tea Party and conservative policy objectives

In January, once the new Congress is sworn in, it will get down to the business of legislating. Granted, business is likely to be halting, particularly if the majorities in each chamber of Congress are narrow (as is likely), or if one party controls the House but not the Senate (as is also somewhat likely). Still, one positive for conservatives is that Tea Party candidates will more reliably oppose the Democratic agenda, and will more reliably support something like an attempt to repeal the health care bill.



Dimension 5: The Tea Party and the Republican “big tent”

The Tea Party also presents longer-term risks to the Republicans. It’s one thing to mount primary challenges in states like Utah and Alaska, which can support (very) conservative Republicans. A party that cannot also support moderates like Mike Castle of Delaware, however, or Rick Lazio of New York –- states with long traditions of moderate Republicanism –- would seem to have limited upside in the majority.

What must someone like Senator Olympia Snowe of Maine, who is under great threat of a Republican primary challenge when she comes up for re-election in 2012, be thinking right now?

Democrats, when they were ascending in 2006 and 2008, had little trouble nominating moderate candidates who were appropriate for specific states or Congressional districts. Some of those candidates, having won office, have since become targets of some on the left, since they do not always support the Democratic agenda. But, at least, Democrats waited until they were in power before the infighting began.

Republicans, however, may be in for a long two years –- even or perhaps especially if they take control of one or both chambers of Congress.

The struggle between establishment and insurgent Republicans will not have been resolved –- instead, it will continue against the background of the battle for the Republican presidential nomination, which is almost certain to be combative. Meanwhile, Republicans may be given relatively more responsibility for the condition of the economy, which may not show much improvement over the next two years. And their efforts to pass legislation may be stymied by a (barely) Democratic Senate and –- where necessary -– by President Obama’s veto pen. If Tea Party supporters are expecting their candidates to facilitate a repeal of the health care bill, or a radical reduction in tax rates, they may be disappointed.

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In some ways, the Tea Party represents an end-around for Republicans -– it may help to facilitate large electoral gains for them in November in spite of a party brand which is badly damaged. Although it may have done harm to Republicans in a few specific races, like Delaware, this may be outweighed by the good it has done them elsewhere in the country.

But there is one fundamental Republican problem that the Tea Party has not resolved: the brand remains extremely unpopular among large segments of the public. In fact, the Tea Party is in some ways a reaction to this: particularly after Delaware, we should probably take the Tea Party at its word that stands in opposition to the Republican and Democratic establishments alike.

How loyal will voters who were inspired by the Tea Party remain to the Republican Party -– and how loyal will Republicans remain to the Tea Party? The relationship is to some extent one of convenience. The Tea Party has candidates full of energy and chutzpah and some fresh-seeming ideas, but it lacks, on its own, the infrastructure to get these candidates elected. The Republican Party, meanwhile -– while short on popular ideas and popular leaders -– has access to money, voter lists, and experienced strategic hands. To some extent, the Tea Party is renting the Republicans’ electoral infrastructure.

But once some Tea Party candidates are in power, what need will they have for the skeleton of the Republican establishment? And how much will the Republican establishment, sensing this, default into self-preservation? Meanwhile, how effectively might the Tea Party differentiate itself from the establishment in the eyes of voters, once it becomes part of the establishment? If the Republican Party is not adroit at navigating these problems, then it is probably in for more punishment from voters –- whether in 2012 or in the future.

What the Tea Party may have helped to ensure, however, is that Democrats will get their punishment first.