A new CNN poll finds that 55 percent of voters have a negative view of the Republican Party, tied for their second-highest unfavorable score since CNN began asking this question in 1992. The Republicans also achieved a 55 percent unfavorable rating in a poll conducted in April 2009, although the party’s all-time high, 57 percent, was recorded as the House of Representatives was in the process of impeaching Bill Clinton in December, 1998.

The news for Democrats is not any better. Some 49 percent of voters now hold a negative view of the party, according to the poll. Although this figure is slightly better than for Republicans, it matches the Democrats’ record high unfavorable rating of September 2010 and is part of an upward trajectory that has persisted for the past three years.

The combined unfavorable score for both parties — 104 percent — is also a record, and represents the first time that the figure has been above 100.

The G.O.P.’s unfavorable score has historically been more volatile than that of the Democrats. On previous occasions when the Republicans’ unfavorable rating spiked, however, like in 1998 and from 2006 through 2008, the Democratic Party’s declined slightly.

Since President Obama was inaugurated in 2009, however, the Democrats’ unfavorable rating have increased substantially without a corresponding drop for the Republicans. (A fine-toothed comb might find a very slight decline in the Republican unfavorable rating between 2009 and 2010, but it appears to be on the rise again now.) Thus, the combined dissatisfaction with the parties has grown steadily and is now about 20 percentage points higher than it was in the 2008 election cycle.

A credible independent bid for the presidency is always a long-shot, but might be more viable under these conditions. Or we may simply see a genuine anti-incumbent wave — a much-discussed phenomenon that has rarely occurred in practice — with significant numbers of elected officials in both parties losing office. It is not out of the question that Democrats could lose the White House but take back control of the House of Representatives.

But there are also downside cases for both the president and the Congress. Mr. Obama’s post-partisan branding, evident especially during the early phases of his 2008 campaign, has been submerged by parties that continue to become more partisan on the one hand and less popular on the other. Just 23 bills have been signed into law by the president this year, a staggeringly low number. The president has scored some tactical points during the debt limit negotiations. But both Democratic and independent voters, for somewhat differing reasons, may question whether his overall strategy has been effective.

For Republicans, meanwhile, there is the possibility that the party’s unfavorable rating, which is up 7 points since March, will continue to grow as it asserts an agenda whose popularity is questionable, especially on issues like changes to entitlement programs. Their favorable rating, 41 percent, is well below that of Democrats in 2007 or Republicans in 1995 after winning control of Congress in those years, leaving the G.O.P. without a clear mandate.