Recent years have seen the Democrats and Republicans evolve into predominantly liberal and conservative parties, respectively, rather than the broad coalitions of the past.

But some current developments suggest neither has achieved total unity and that internal conflicts threaten both parties’ short-term goals — and possibly their long-term ones.

For the Democrats, resistance from their more conservative members, mainly from Republican-leaning states in the South, the Plains and the Mountain West, threaten passage of the health care bill, President Barack Obama’s top legislative priority.

For the Republicans, conflict between conservative purists and their more pragmatic faction could undercut efforts to rebound from sweeping electoral defeats in the past two elections.

Third-party candidates with Republican backgrounds are threatening the GOP’s chances of winning two of next month’s three main races, and internal conflicts are emerging as potential 2010 problems, especially in such key states as Texas and Florida.

This could presage problems for Republicans when they choose a 2012 opponent for Obama.

Significantly, the Republicans are unified this year in the race for governor of Virginia, and that currently looms as its likeliest Nov. 3 success. All party elements coalesced early around Bob McDonnell, a conservative who has downplayed social issues and stressed the economy, jobs and criticism of Obama’s spending proposals.

This has played well in Virginia, still a conservative state despite Obama’s 2008 victory and consecutive Democratic gubernatorial triumphs. Democrat Creigh Deeds, a weak campaigner, has encountered difficulty in attracting the black votes so crucial to Obama’s victory.

Elsewhere, GOP unity has been absent.

In New Jersey, the other state electing a governor, independent Chris Daggett, a former GOP state and federal official, has gained support by stressing fiscal issues and attacking his two rivals, Democratic Gov. Jon Corzine and Chris Christie, a Republican former U.S. attorney.

If Daggett can maintain his current support, always a question with independents, Corzine could survive in what has become a generally Democratic state.

The most acrimonious GOP split has occurred in a special congressional election in upstate New York, where Republican Dede Scozzafava’s support for abortion rights and gay marriage have fueled a strong bid by Doug Hoffman, running on the Conservative Party label.

The sprawling rural district has not elected a Democrat since 1871, though Obama narrowly carried it last year. In the most recent independent poll, Democrat Bill Owens narrowly led the three-way contest for the seat vacated when the president named incumbent John McHugh as secretary of the Army.

Democratic success in one or both of the three-way races would prevent the GOP from being able to claim voters had repudiated Obama.

On balance, the midterm election landscape tends to favor the opposition party, and GOP leaders hope for a reaction against Obama’s proposals to increase federal spending and expand health care and environmental programs. But the recurring ideological divisions could hobble the GOP effort.

The Democrats have encountered their own internal difficulties on Obama’s health care bill, exacerbated by the soaring federal budget deficit and public resistance to expanding governmental programs.

Senate Finance Committee chair Max Baucus’ delicate legislative craftsmanship was aimed as much at gaining the support of Democrats Ben Nelson of Nebraska, Blanche Lincoln of Arkansas, Mary Landrieu of Louisiana and Evan Bayh of Indiana as at wooing Republican Olympia Snowe of Maine. With just 60 Democrats in the Senate and Republican support likely to be minimal, Democratic leaders may need all of those votes to overcome a Republican filibuster.

Meanwhile, House leaders’ determination to include the provision for a “public option” in its health bill could cost enough conservative Democratic votes to make the outcome close, despite a 38-seat Democratic majority.

The GOP’s election dilemmas, and the ones faced by congressional Democratic leaders, are reminders that, despite substantial ideological realignment, the U.S. remains far different from countries where the electorate’s decision to install a parliamentary majority ensures passage of its major initiatives.