Washington, D.C. -- While no one has officially declared a run for president in 2016, many of the likely candidates already are working hard on the campaign trail. Stumping for members of their own party during the midterms is the easiest way to boost exposure and build favors among politicians whose endorsements they will be courting less than two years from now.

“Anyone thinking of running for president wants to expand their brand to potential activists, donors and voters in general,” Republican strategist Greg Mueller said. “While these popular politicians are certainly out to help and support like-minded candidates, the effort is also a downpayment on any potential run for the presidency.”  

New Jersey Gov. Chris Christie, head of the Republican Governors Association, has gone to Florida to campaign for Rick Scott and to Illinois to stump for Bruce Rauner. In the week before Election Day he'll hit Maryland, Rhode Island, Maine, Arizona, New Mexico, Colorado, Wisconsin and Ohio.

He'll also spend time in Iowa, which holds the first presidential caucus and plays a key role in picking nominees.

Christie's road trip demonstrated his ability to energize a crowd and draw media attention. It also exposed the dangers for high-profile campaign surrogates -- like overshadowing the local candidate, or creating a personal negative news cycle.

Despite Christie's efforts to focus attention on Scott at a Florida campaign stop last weekend, reporters wanted to talk about the New Jersey governor's decision to quarantine a nurse who'd returned from treating Ebola patients in West Africa. Scott just stood by, mostly silent, while Christie talked about the issue facing his own state. 

Hillary Clinton has also had an ambitious midterms itinerary -- and a misstep. Last week she was rallying voters for Massachusetts gubernatorial candidate Martha Coakley.

"Don't let anybody tell you that it's corporations and businesses that create jobs," she said as part of a riff about the problem with trickle-down economics. The remark raised echoes of President Obama's "You didn't build that" comment in 2012, which played into a Republican narrative that Democrats are anti-business. That's not a charge Clinton wants to draw.

Back in New York Monday to campaign for Rep. Sean Maloney, who worked as an aide to President Bill Clinton, Hillary Clinton did damage control.

"Let me be absolutely clear about what I've been saying for a couple of decades: Our economy grows when businesses and entrepreneurs create good-paying jobs here in an America where workers and families are empowered to build from the bottom up and the middle out -- not when we hand out tax breaks for corporations that outsource jobs or stash their profits overseas," she said.

Clinton will be working hard in the next week, including hitting early primary states. She'll make two stops in Iowa to campaign for Senate candidate Bruce Braley, an appearance for Sen. Mary Landrieu in New Orleans Saturday and will head to New Hampshire Sunday to campaign for Sen. Jeanne Shaheen and Gov. Maggie Hassan. She campaigned with North Carolina Sen. Kay Hagan last week.

Demonstrating the power of the endorsement, Clinton will be in Maryland Thursday stumping for gubernatorial candidate Anthony Brown, who backed her presidential campaign early in 2008. 

Clinton and Christie are the highest-wattage 2016ers on the campaign trail, but not the only ones.

Republican Jeb Bush went to South Carolina last week to support Gov. Nikki Haley. He went to Kansas to campaign for Sen. Pat Roberts. And in his own backyard, Bush has been working to boost Scott’s bid for re-election.

Democrat Martin O’Malley, the Maryland governor, stumped for candidates in the past when he served as the head of the Democratic Governors Association. Last week, O’Malley visited New Hampshire to campaign for Shaheen and Hassan. 

Louisiana Republican Gov. Bobby Jindal, who appears to be holding on to 2016 aspirations, also hit the campaign trail. On Monday, he campaigned for Kansas Gov. Sam Brownback. Later this week he will head to Florida to campaign for Scott and then to Kentucky to campaign with Senate Minority Leader Mitch McConnell. But Jindal has stayed out of the Louisiana Senate race, where Republican Bill Cassidy is trying to unseat Landrieu. Jindal hasn’t endorsed or campaigned for his fellow Pelican State Republican. That may be because local tea partiers are still backing another GOPer, Rob Maness. Why alienate voters that you might want to woo in 2016? 

Democrat Elizabeth Warren, who has said she doesn't plan to run in 2016, has been a popular draw on the campaign trail. She stumped for Shaheen last week -- a tailor-made role since Warren defeated Scott Brown in Massachusetts the last time he ran. Warren headed to Kentucky Tuesday to campaign for Alison Lundergan Grimes

And some potential 2016 candidates are sending money instead of showing up in person. Rand Paul’s PAC RandPac announced Tuesday a six-figure ad buy to help Roberts in Kansas. He’s also bought online ads to try to help in other races, including Kentucky, New Hampshire, Iowa and North Carolina.