WASHINGTON (AP) -- A resurgent Mitt Romney is popping up more in other Republican candidates' ads as both parties press their closing arguments in closely contested Senate races.
President Barack Obama continues to be referenced in negative ads aimed at boosting GOP candidates. His own party's Senate hopefuls are keeping their distance from the president, turning to Bill Clinton when they feel the need for a presidential embrace.
The tactics reflect that a huge part of this year's battle for control of the Senate is being waged in conservative-leaning states such as Montana, North Dakota, Arizona and Indiana, where the candidates are hoping Romney's uptick in polls will propel their candidacies as well.
"The stakes are high, Montana. I urge you to send Denny to the Senate and we'll get America back on track," Romney says in the latest ad from Republican Denny Rehberg. Romney cut a similar ad for Senate candidate Jeff Flake of Arizona and had already appeared in a spot for Republican Richard Mourdock of Indiana.
Some outside groups also are incorporating the presidential race into their final Senate ads.
"With Mitt Romney as president, we can get our country back on track, but not with Heidi Heitkamp in the Senate," says the latest ad in North Dakota from Crossroads GPS, started by former George W. Bush political adviser Karl Rove. The group is hoping its ads will help Republican Rick Berg prevail.
The strategy for the Democratic candidates in these conservative-leaning states is to display a strong sense of independence. They need to get voters to split their tickets to prevail. That means no images of Obama and a laser-like focus on coming across as someone who will work across party lines to do what's best for the state. Heitkamp's latest ad talks about her roots growing up in the small town of Mantador.
Overall, the Senate Republicans' party apparatus is advertising in eight states in the final week: Arizona, Indiana, Montana, North Dakota, Nevada, Ohio, Virginia and Wisconsin.
Senate Democrats' party operation is airing ads in those states, too, plus two others: Connecticut and Missouri.
Taken together, the ad wars sketch out a map of where the battle for the Senate is likely to be won.
Whether the late wave of ads can break through the media clutter and provide an edge won't be known until after the polls close Election Day, but some big ad buys are drawing attention:
—American Crossroads, a super PAC organized by Rove, and its affiliate, Crossroads GPS, are making a big push over the final week, flooding the airwaves with $10.5 million in ads airing in Maine, New Mexico, Nevada, North Dakota, Ohio, Virginia, Indiana, Montana, Nebraska and Wisconsin.
—Democratic-aligned Majority PAC is countering with a $7 million ad blitz targeting Montana, Wisconsin, Indiana, North Dakota, Virginia, Connecticut and Florida.
—American Crossroads is pumping $420,000 into Nebraska's tightening Senate race to shore up Republican Deb Fischer as she tries to turn back Democrat Bob Kerrey's bid to return to the Senate.
The closing arguments in ads from both sides are a mixed bag. Republicans cast Democrats as supporters of big government, higher taxes and exploding deficits. Democrats fire back that Republicans are conservative extremists, beholden to special interests and eager to slash key social programs.
Democrats have a 53-47 advantage in the Senate, including two independents who align with them. About a dozen of the 33 seats on the ballot are seen as competitive, most in the West and Midwest. Republicans need a net pickup of four seats to take control if Obama is re-elected, three if GOP presidential candidate Mitt Romney wins, since the vice president gets a tie-breaking vote.
In many cases, the final messages reflect the uniqueness of the states. An ad by Republican Sen. Scott Brown touts his independence in Democratic-dominated Massachusetts against Elizabeth Warren, who has a slight edge. Republican Senate candidate Linda McMahon in Connecticut has an ad urging Obama supporters to also vote for her in a state where Obama has a wide lead.
Former Surgeon General Richard Carmona, running as a Democrat in conservative Arizona, appeals to independent voters, about a third of the electorate. "Let's just get somebody there who will listen and start solving some problems," he says in his latest ad.
Republican opponent Jeff Flake's final pitch shows images of him with the state's two GOP senators, John McCain and Jon Kyl, as well as with Romney. Carmona is shown with Obama and House Democratic leader Nancy Pelosi. "It's a choice," the ad's narrator says.
While Democrats rarely refer to Obama, Democrat Tammy Baldwin in Wisconsin features Clinton in a commercial that aims to harness some of the former president's star power in her tight race against Republican Tommy Thompson. Thompson's latest ad features a testimonial from his wife.
Republican efforts to nationalize races in conservative-leaning states have been frustrated in Indiana and Missouri, where the GOP candidates have stumbled as they discussed their opposition to abortion in cases involving rape.
Democratic Sen. Claire McCaskill's latest ad in Missouri features women talking about Republican Todd Akin's comment that women have the ability to avoid pregnancy during a "legitimate rape."
"Todd Akin is scary," said one of the women featured in the McCaskill's ad. "I'm afraid of what he'll do in Congress."
Akin is trying to steer voter attention back to the economy, making the case that he would lower taxes as a way to spur job creation.
In Indiana, Republicans fear that Mourdock's debate comment that pregnancy resulting from rape is "something God intended" could derail their hopes. An ad for Democrat Joe Donnelly meshed several Mourdock statements to portray him as outside the mainstream.
"And Richard Mourdock's opinions: Pregnancy caused by rape is something 'God intended.' He says Medicare and Social Security are unconstitutional," the narrator says.
The Mourdouck campaign replies, "Donnelly and his liberal allies have gone too far, attacking Richard Mourdock's religious faith and twisting his words, playing politics and distracting from the real issues, such as stopping the Democratic House and Senate leaders' agenda."