Given the way American voters currently evaluate the two political parties and President Bush, 2008 has the makings of another good Democratic year.

Coming off a dramatic sweep in the 2006 midterm elections, when they took control of both the U.S. House of Representatives and the U.S. Senate, Democrats continue to have momentum. The president remains widely unpopular, the Iraq War shows few signs of either winding down or improving, economists express concern about the economy and the Republican Party has picked up plenty of baggage over the past seven years.

House and Senate retirements also are working against the GOP, as is the partisan distribution of seats up in the Senate next year. Just as bad for Republicans is Democratic enthusiasm and fundraising, both of which are far greater than the Republicans’.

But Republicans are not throwing in the towel just yet, nor should they. A stronger-than-expected showing by the Republican nominee in a Massachusetts Congressional special election combined with the GOP’s takeover of the Louisiana governorship last month shows that reports of the GOP’s death have been greatly exaggerated. And Congress’ low job-approval rating suggests that some Democrats could be on the receiving end of an election when Americans vote for change.

In addition, Republicans have at least some reason to expect that the 2008 presidential race will be a close, hard-fought battle that they can win, even if they begin it as underdogs.

Still, neither the House nor the Senate currently seems headed to return to GOP control after next year’s balloting, and Republicans have reason to fear that they could experience another wave of losses in both chambers.

Republicans need to net 16 seats to regain a majority in the House, and the combination of strong Democratic recruiting, a substantial Democratic fundraising advantage and the Democratic Party’s advantage on a number of key issues, including the Iraq War and health care, should make it difficult for the GOP to gain much ground.

Republicans lost a handful of seats in 2006 that should rightly be theirs, and they will have an excellent opportunity to win some of those seats back. They also are hoping voters believe that Democrats have not done much since they won control of Capitol Hill a year ago. It’s already clear that Republicans hope to brand Democrats as supporting higher taxes, bigger government and a foreign policy/homeland security agenda that makes Americans less safe.

But the Democratic Congressional Campaign Committee’s huge financial advantage — the committee had more than $28 million in the bank compared with less than $2 million on hand by the National Republican Congressional Committee — means Democrats can play both offense and defense in the fight for the House if they have to.

Retirements are beginning to look like a considerable GOP problem as well. Not all of the party’s open seats will be difficult to hold, but the party already has seen a number of retirements from competitive districts, either because Members don’t enjoy being in the minority in the House or because statewide races seem more appealing.

In particular, GOP open seats in New Mexico, Minnesota, Ohio and Arizona already look at some risk, and more retirements are likely later this year and early in 2008.

While both parties have some strong recruits, Democrats are fielding interesting candidates in a number of districts they contested only halfheartedly last year, and a considerable number of repeat Democratic challengers who came up just short in 2006 are back for another try in 2008, this time with experience as candidates and far greater fundraising potential.

The Senate looks like anything from a Republican problem to a disaster waiting to happen. At least three of the five GOP retirements (in Virginia, Colorado, New Mexico, Nebraska and Idaho) are at risk, with the Republican nominees likely to start off trailing in at least three of those states.

A number of other incumbent Republican Senators who are seeking re-election are at considerable risk, in part because of the strength of the Democratic challengers and in part because the states themselves are difficult ones for any statewide Republican candidate. Democrats begin with a narrow edge in New Hampshire and have very real chances in Oregon, Maine and Minnesota, all states carried by Sen. John Kerry (D-Mass.) in the 2004 presidential election.

With Democrats likely to maintain control of both chambers of Congress, the GOP’s sole hope of dictating the policy discussion in the nation’s capital in 2009 rests on the fight for the presidency. And again, the early line favors the Democrats.

After eight years of a Republican president, Democrats have the “time for a change” argument going for them. Voters clearly are unhappy with Bush’s performance in office, and they no longer give his party high marks on foreign policy, taxes or the economy, issues on which the GOP once held a decisive advantage over Democrats. In fact, Democrats hold advantages as the party better able to deal with most issue areas.

Fundraising by Democratic presidential candidates has far exceeded GOP presidential fundraising, another measure of party optimism and energy.

Luckily for the GOP, they have two things going for them.

First, all of the Republican presidential candidates are able to run, in one way or the other, as political outsiders. None has been in the Bush administration.

Sen. John McCain (Ariz.) has been in Washington, D.C., for years, but he always has been a maverick who spoke his own mind, even if party leaders objected to his view. Former Massachusetts Gov. Mitt Romney and former New York Mayor Rudy Giuliani have not served in Congress and therefore are able to run “against” Capitol Hill. And former Sen. Fred Thompson (Tenn.) has spent a few years out of the political business.

The Republicans also figure to be able to run against the eventual Democratic nominee. Sen. Hillary Rodham Clinton (N.Y.) is a polarizing figure who has high negatives, while Sen. Barack Obama’s (Ill.) lack of experience and former Sen. John Edwards’ (N.C.) liberalism also would be obvious GOP targets.

Still, given the closeness of the 2000 and 2004 presidential elections and the deterioration of the Republican Party’s standing, the eventual Democratic nominee is likely to begin with at least a slight advantage next year. And each of the Republican candidates has problems, including, in the case of Giuliani, such strong opposition among the GOP base that his nomination could well generate a third-party, conservative candidate.

At this point, it is the Democrats who appear to have the upper hand, certainly in the fight for the presidency and for the Senate, and probably for the House, and Democratic control of both chambers of Congress and of the White House seems like the single most likely scenario after the 2008 elections.