President Barack Obama and Vice President Joe Biden have a lot to catch up on. 

Just back from two weeks of vacation on the tony Massachusetts island of Martha's Vineyard, Obama is holding his weekly lunch with Biden Monday. 

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While the president has been away, Biden has been ramping up discussions about whether he will seek the Democratic presidential nomination in 2016. 

If Biden runs, it would put Obama in an awkward position. 

Hillary Rodham Clinton, his former secretary of state, is currently the front-runner in the Democratic primary, but she's been plagued with questions about her use of personal email and a private server while in government. 

It's all but certain that Obama would not endorse a candidate in the primary if both Biden and Clinton run.