Republicans are celebrating two high-profile electoral successes last Tuesday; Democrats are licking their wounds. But the results and dynamics revealed long-term problems for both national parties.

For the Democrats, diminished enthusiasm among independent, young and minority voters raises questions about whether the coalition that elected President Barack Obama will help the party fend off significant losses in next year’s more important midterm congressional and state elections.

It was a major factor in the party losing the Virginia and New Jersey governorships.

For the Republicans, the aggressive stance of its conservative base and resulting fallout suggests the GOP may be headed down a historical path in which an energized base takes control of a defeated party with disastrous national results, at least in the short term.

The split created by that effort gave the Democrats an unexpected victory in a closely watched upstate New York special congressional election.

Off-year elections, especially in so few places, can only hint about the future. Obama’s failure to prevent GOP victories in Virginia and New Jersey suggests a limit to his coattails that might unsettle Democratic senators and congressman seeking to enact his legislative proposals, especially health care reform. Yet exit polls also showed that voters said Obama was a minor factor.

In Virginia, Republican Bob McDonnell ran a good campaign that attracted independents, while Democrat Creigh Deeds ran a poor one that turned off Obama Democrats. In New Jersey, Democratic Gov. Jon Corzine’s unpopularity proved too big a hurdle in a race where a third candidate’s support faded, as often happens in the stretch.

In each state, the electorate was significantly different from last year’s, with proportionately more older voters and fewer minorities and younger voters. The bad news for Democrats next year is that such smaller turnouts are the norm in most mid-term elections.

A bigger question may be the impact on legislators in close races, often jittery about controversial votes. But Deeds’ poor showing might remind vulnerable Democrats there is little to gain through separation from Obama since a successful president can help mobilize the base and raise funds, even if he lacks measurable coattails.

For the Republicans, Conservative Party candidate Doug Hoffman’s defeat in the New York congressional race seems unlikely to deter conservatives who contend that the party must offer a clear choice.

But as happened, a rightward swing might drive away moderates and replicate a potentially perilous pattern. Three times in the past half-century, a party’s national defeat prompted its base to seek greater ideological purity in the next election.

In two cases, the outcome was a resounding defeat.

Sen. Barry Goldwater’s conservative followers in 1964 vowed to offer “a choice not an echo” after John Kennedy’s narrow 1960 presidential victory. Goldwater carried just six states, but Republicans rebounded in 1968 with a more centrist approach.

In 1972, fervent anti-Vietnam War Democrats spearheaded liberal Sen. George McGovern’s nomination. He won just one state and the District of Columbia. But in 1976, the far more conservative Jimmy Carter enabled Democrats to regain the presidency.

In the exception, Ronald Reagan led a conservative takeover in 1980 that unseated Carter, whose presidency was undercut by inflation at home and weak leadership abroad.

GOP conservatives hope to follow that example in 2012. Success may hinge on a public sufficiently disaffected with Obama and a Republican candidate like Reagan whose personal appeal extends beyond his ideological appeal to the base.

Whether any prospective Republican fits that definition remains to be seen. So does the ultimate public verdict on Obama, who remains more popular than his policies.

A more fruitful GOP course may be that of the two gubernatorial winners. Despite conservative roots, McDonnell played down social issues and focused on economic subjects like jobs and spending, as did Christie.

Their success suggests a way Republicans can woo the independents and less committed partisans they’ll need to win in the future.