With Election Day just one week away, anxious Democrats insist that early voting returns in key Senate races from West Virginia to California offer cause for optimism. While the numbers also leave room for debate, it’s clear that the electoral landscape in several competitive Senate contests is far from settled.

‘Republicans have turned themselves into meteorologists forecasting dark storm clouds, tidal waves, and tsunamis. But like the weather, politics can be difficult to predict,’ Democratic Senatorial Campaign Committee Chairman Bob Menendez (N.J.) wrote in a campaign memo about early voting distributed Monday. ‘Despite national momentum being on the Republican side for months, we are not seeing anything resembling a Republican surge. In fact, to the contrary, in key Senate races, we are seeing encouraging signs for Democrats. Granted this analysis accounts for only one full week of early vote data, we believe our modeling shows that Democrats are engaged, enthused ‘ and most importantly ‘ voting.’

Republicans need to flip 10 seats to assume control of the Senate, a possibility that Menendez’s Republican counterpart, Sen. John Cornyn (Texas), has repeatedly deemed a ‘two-cycle process.’

But a GOP takeover is not unthinkable, and major gains are all but assured. Republicans’ hopes, of course, are tied to the ‘enthusiasm gap’ that they believe will deliver far more conservatives to the polls on Nov. 2.

Early voting statistics offer just one measure of the enthusiasm among two parties, and recent polling offers another. Political strategists from both parties, meanwhile, are trying to do everything in their power to influence turnout among their bases.

[IMGCAP(1)]The campaign committees and outside groups are diverting tens of millions of dollars to the effort. President Barack Obama and his surrogates will criss-cross the country in the coming days. And the tea party movement will supplement a bus tour with rallies and a television advertising campaign to support its picks in Nevada, Alaska and Delaware, among others.

‘Really, it’s full speed ahead with as much energy and focus as we can muster,’ Levi Russell, spokesman for the Tea Party Express, said in a telephone interview as his campaign bus sped down a drag-racing strip in Texas on Monday afternoon. The bus will be in Delaware by the end of this weekend.

Base Voters Come Home

Early voting ‘ a process that accounted for roughly 30 percent of all ballots cast in 2008 ‘ is offered in more than 30 states and has become a focus for both parties this cycle.

‘You need to go right after this rally, fill out that ballot and mail it in,’ Obama said last week at a Seattle rally for Sen. Patty Murray (D). ‘Today. Not tomorrow, not the next day, but today.’

Through the first week of early voting, Democrats cast more ballots than Republicans in West Virginia, California, North Carolina and Iowa. The turnout is roughly even in the key states of Illinois and Nevada.

‘Now that voters are casting ballots, we can see our work has been effective,’ Menendez wrote, citing the early voting statistics.

Republicans largely laughed off the chairman’s analysis.

‘Republicans could only hope that Senate Democrats seriously believe their own spin on this matter,’ said Brian Walsh, spokesman for the National Republican Senatorial Committee. ‘The states they cite are states that already have a strong party advantage for Democrats. … The issue in states like California and Nevada is what are independents going to do?’

Republican pollster Gene Ulm of Public Opinion Strategies also pointed to the level of Democratic enthusiasm, especially in a state such as California, where Democrats hold a 13-point voter registration advantage. With 12 percent of registered voters already reporting, Democrats held a 4-point lead in the number of ballots returned.

‘You have a bunch of base Democrats. Sooner or later, you know they’re going to come home,’ Ulm said. ‘African-Americans are going to come home. But are there going to be fewer of them? Yeah.’

Republicans point out that Menendez’s optimism about early voting assumes that registered Democrats are voting for Democrats. This year, Walsh said, that’s not at all a safe assumption, especially in a place like West Virginia, where just 31 percent of likely voters approve of Obama’s job performance, according to a Public Policy Polling survey released Monday.

Driving Turnout

As of Monday evening, West Virginia was among six states Roll Call listed as Tossup. The others include Pennsylvania, Illinois, Colorado, Nevada and Washington.

But political conditions are constantly shifting in those states, and second-tier races may prove to be equally competitive.

The NRSC, for example, acknowledged plans to spend $3 million on independent expenditures in California in the coming days. That’s hardly the strategy of a party that believes a race is out of reach, even though Sen. Barbara Boxer (D) has led consistently in public polling and has a cash advantage.

In Pennsylvania, where Rep. Joe Sestak (D) had trailed in virtually every public poll since May, various polls showed him within the margin of error last week.

An internal memo from Senate hopeful Pat Toomey’s pollster showed that the Republican believed the race had tightened weeks ago. But pollster Jon Lerner noted that two polls released since Friday give Toomey the advantage again.

‘Notably, however, just as observers mistook Sestak’s gradual consolidation of the Democratic base vote for a sudden shift in his favor, they are now also missing the shift that is taking place in Toomey’s direction,’ Lerner wrote. ‘Sestak has no more room to grow his numbers among strong partisan Democrats, and he is failing to capture voters in the center of the electorate.’

Both Obama and the tea party movement will fight to rally their bases in the coming days.

Senate Democrats are pleased with the president’s campaign schedule so far. Obama has visited Washington, California and Nevada in recent days. After a brief fundraising trip to Rhode Island on Monday, he is scheduled to travel to Pennsylvania on Saturday, followed by stops in Connecticut and Illinois. Each state features a competitive Senate contest.

The Tea Party Express, meanwhile, will make trips to Nevada, California, Washington and Delaware, among other states, before Election Day.

‘We’re doing everything we can to drive a massive turnout,’ Russell said.