Usually, this column takes a granular approach to politics. Most often, we’re handicapping gubernatorial and legislative races. But for this one time, we’re taking a look at the big picture in American politics today -- the really big picture.

While there’s no single theory that can explain all political behavior in America, there’s still reason to believe that distinct patterns are emerging at four different levels of government, and that those patterns are almost perfectly balanced by party.

Let’s start at the presidential level, where demographic patterns are making it increasingly challenging for the Republican Party to win the White House. By the same token, structural factors are making it increasingly difficult for the Democrats to take control of either chamber of Congress.

Meanwhile, state elections timed for the midterm cycle will continue to make it hard for Democrats to win governorships, and local demographic and political shifts will make it increasingly harder for Republicans to win mayoral elections.

Put it all together and each party should have an edge in two political arenas -- the Democrats with the White House and mayoral offices, and the Republicans in congressional and gubernatorial elections. Depending on your perspective, this is either a recipe for long-term gridlock or an opportunity for each party to enact its agenda at a different level of government.

Let’s take a closer look, level by level.

The Presidency

Simply put, Democrats have an edge in the Electoral College, though it’s not an insurmountable one.

Here’s how: Any credible Democratic candidate would start with an almost certain base of 170 electoral votes (California, Connecticut, Delaware, the District of Columbia, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island and Vermont). It’s probably safe to add another 27 electoral votes (Minnesota, New Mexico and Washington state). Together, that adds up to 197 votes. If you add in three swing states that haven’t voted Republican for president since 1988 (Maine, Michigan, Pennsylvania and Wisconsin) that gets a Democratic nominee up to 247, or just 23 swing-state electoral votes short of the 270 needed to win the presidency.

By contrast, the Republicans start out with 143 solid electoral votes (Alabama, Alaska, Arkansas, Idaho, Kansas, Kentucky, Louisiana, Mississippi, Montana, Nebraska, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia and Wyoming). It’s also reasonable to add four Republican leaning states with a collective 48 electoral votes (Arizona, Georgia, Indiana and Missouri). Together, that’s 191 electoral votes, or 206 if you include North Carolina, which voted Republican in five of the last six elections. This lineup requires the GOP to win 64 swing-state votes -- almost three times as many as the Democrats would need.

In 2012, Obama eventually got 332 electoral votes to win re-election. (AP/David Zalubowski)

Under this scenario, the swingiest of the swing states, which we’ve categorized as belonging to neither party’s lineup, control the 85 pivotal electoral votes -- Colorado, Florida, Iowa, Nevada, New Hampshire, Ohio and Virginia.

In reality, it’s not at all clear that the GOP will inevitably lose Maine, Michigan, Pennsylvania and Wisconsin for the foreseeable future, meaning that Democrats don’t actually have a lock on the presidency. Still, for Democrats, it’s a nice edge to start with, and more important, it’s fortified by demographic changes helpful to their party.

As political analysts Charlie Cook and David Wasserman recently noted, the racial and ethnic diversification of the electorate continues. Cook and Wasserman foresee the likelihood that the white share of the electorate, which forms the core of the Republican Party, will shrink from 72 percent in 2012 to 70 percent in 2016. Those two lost percentage points would be redistributed to Hispanics and Asian-Americans, two groups more favorable to Democratic candidates. “If the 2012 election had been held with that breakdown (keeping all other variables stable), President Obama would have won by 5.4 percentage points rather than by his actual 3.85-point margin,” Cook and Wasserman write.

They add that “the group with which the GOP does best -- whites without college degrees -- is the only one poised to shrink in 2016. ... In other words, the GOP doesn't just have a growing problem with nonwhites; it has a shrinkage problem as well, as conservative white seniors are supplanted by college-educated millennials with different cultural attitudes.”

While this doesn’t equate to a recipe for certain victory, it’s not a bad position to be in if you’re a Democrat.

Congress

Where the Democrats have an edge in the presidency, Republicans have the advantage in Congress.

This is clearest in the House. The clustering of Democratic voters in densely populated urban areas means that any reasonably compact district will likely include many “wasted” Democratic votes -- that is, Democratic support levels far above 51 percent in a given district, which could otherwise be used to dilute Republican strength in neighboring districts. This clustering was exacerbated by a strong Republican election cycle in 2010, when voters, even in otherwise Democratic-leaning states, elected GOP legislators and governors who proceeded to draw district lines favorable to the GOP. This is a key reason why a purple-to-blue state like Pennsylvania has a 13-5 Republican lead in its House delegation and why a swing state like Florida has a 17-10 GOP edge.

The combination of clustering and redistricting has produced a House electoral landscape in which few seats are genuinely competitive. To become a majority in the 435-member chamber, a party must assemble at least 218 votes. Currently, the House GOP has a 246-188 edge, not counting one vacant seat. As of now, the Cook Political Report has rated just 29 seats as competitive, either as tossups or as leaning toward one party or the other. That’s not even enough competitive seats to sway the balance of power.

This statistic shows how hard it will be for Democrats to take back the House anytime soon -- but it gets even worse for the party. Of those 29 competitive seats, only 22 are Republican-held. So, the Democrats would not only have to hold onto their own seven endangered seats, but would have to sweep every single one of the competitive Republican-held seats and then flip eight more GOP-held House seats that aren’t currently considered competitive -- all in order to achieve a bare, one-seat majority.

Securing a Democratic majority more solid than that would require even more seats, which is tough when so few seats in either party are even remotely competitive. Just four House GOP winners in 2014 failed to get to 50 percent; another nine won with 50 or 51 percent; and another 10 won with between 52 and 55 percent of the vote. All told, that’s less than 10 percent of the GOP caucus that had even vaguely close races in 2014.

Obama delivering his State of the Union address to a joint session of Congress. (AP/Pablo Martinez Monsivais)

Superficially, the Senate offers more hope for Democrats. The map of seats being contested in 2016 is favorable to the Democrats, with the GOP having to defend more incumbents and open seats, and many of those elections taking place on reasonably favorable territory for the Democrats. Because of this, Senate Democrats have a real chance of seizing the chamber in 2016, just two years after losing it.

If you take a longer, more structural view, though, the situation is less rosy for the Democrats in the Senate. That’s because the Senate gives equal weight to states, not to population. To explain, let’s give each party two Senate seats for its “strong” states, and split the two Senate seats between the parties for the 12 swing states. How does this shake out? Using these presidential preferences as a guide, Republicans would have 46 seats in the strong states and another 12 in swing states. That’s 58 seats, or just two short of a filibuster-proof majority. The Democrats, by contrast, would have 30 seats in strong states and 12 in swing states, for just 42 seats total, dooming them to long-term minority status.

While incumbency can certainly keep a state’s weaker party in a Senate seat, retirements and deaths in office eventually give the state’s dominant party a good shot at taking that seat back. And given the geographical structure of the Senate, this favors the GOP.

Governors

The biggest surprise on this list may be the outlook for gubernatorial elections. Here, Republicans have reason for optimism.

Historically, gubernatorial elections have tended to be up for grabs between the parties. Statewide electorates are sufficiently eclectic to encourage candidates in both parties to run toward the center, expanding their bases. But the pattern of results is changing, and for an unexpected reason.

For obscure reasons, 36 states hold their gubernatorial contests during midterm cycles. This hasn’t seemed to matter much in the past. But in recent elections, the types of voters who cast ballots in midterm elections has diverged significantly from those that do in presidential cycles. Midterm electorates tend to be smaller, whiter, older and more Republican; presidential electorates tend to be larger, more demographically diverse, and more Democratic.

This pattern helped Republican gubernatorial candidates in 2010. That year, the GOP won governorships in such bluish states as Maine, Michigan, New Mexico and Wisconsin. But it proved to be an even bigger help in 2014, another GOP wave year. On the eve of the 2014 election, Governing’s final handicapping of the gubernatorial seats included an unusually large field of 12 tossup races. In a neutral environment, one would expect these races to go roughly half to one party and half to the other. Instead, Republican candidates won eight of those 12 races, plus another contest in Maryland that had been rated lean Democratic. Highly vulnerable Republican incumbents, such as Sam Brownback in Kansas, Scott Walker in Wisconsin, Rick Scott in Florida and Paul LePage in Maine, also won new terms, buoyed by the GOP-friendly electorate.

Currently, the breakdown of the gubernatorial ranks is 31 Republicans, 18 Democrats and one independent. Historically, the number of Republican governors has only been that high on rare occasions, so it’s likely that the GOP number will fall somewhat in the coming years, especially after the 2018 election, when a number of two-term Republican governors will be term-limited out, creating competitive open seats. Still, on balance, it’s going to be a tough challenge for Democrats to take back governorships when so many of them are contested during midterm election cycles.

Mayors

As we’ve noted before, the GOP is having an increasingly difficult time winning mayoral races in big cities. Of the nation’s most populous cities, only a few have Republican mayors. They include three city-county hybrids where suburban voters can play an outsized role (Indianapolis, Jacksonville, Fla.; and Miami), and a few Sun Belt cities (Albuquerque, N.M.; Fort Worth, Texas; Oklahoma City and San Diego). Gone, apparently, are the days when a Republican like Rudy Giuliani could be the mayor of New York or Richard Riordan could be the mayor of Los Angeles.

Here, as with the U.S. House, geography is destiny. Cities have been magnets for younger, more diverse populations that tend to be socially liberal. This makes the Republican Party, with its national image of social conservatism, a tough sell. Indeed, such mayors as Bill DeBlasio of New York, Ed Murray of Seattle and Bill Peduto of Pittsburgh have been pursuing agendas that are unapologetically progressive.

Democratic Mayor Bill Peduto of Pittsburgh (David Kidd)

The clearest example is the spread of minimum-wage hikes. Already, Los Angeles, San Francisco and Seattle have set themselves on a course to raise the minimum wage to $15. Chicago’s is set to rise to $13. By contrast, President Obama got nowhere in Congress with his longstanding efforts to institute a more modest raise to $10.10.

The minimum-wage debate highlights a key consequence of the parties’ varying holds on the levers of power: When stymied at one level, you can try another. Just as Democratic mayors are sidestepping GOP opposition to minimum-wage hikes in Congress, Republican governors are trying to block what they don’t like from Obama’s Democratic administration, such as elements of the Affordable Care Act or action on climate change.

Whether such combat is a boon for federalism -- or a recipe for conflict between the branches -- is in the eye of the beholder. Either way, the multipolar skirmishing between the two parties may well be with us for many years to come.