president before the beginning of the convention. Reagan's supporters then unsuccessfully sought to amend the convention rules so that Gerald Ford would be required to name his vice presidential running mate in advance as well. This move backfired to a degree, as Schweiker's relatively liberal voting record alienated many of the more conservative delegates who were considering a challenge to party delegate selection rules to improve Reagan's chances. In the end, Ford narrowly won the presidential nomination and Reagan's selection of Schweiker became moot. In the 2008 Democratic presidential primaries which pitted Hillary Clinton against Barack Obama, Clinton suggested a Clinton–Obama ticket with Obama in the vice president slot as it would be "unstoppable" against the presumptive Republican nominee. Obama rejected the offer outright, saying, "I want everybody to be absolutely clear. I'm not running for vice president. I'm running for president of the United States of America" while noting "With all due respect. I won twice as many states as Senator Clinton. I've won more of the popular vote than Senator Clinton. I have more delegates than Senator Clinton. So, I don't know how somebody who's in second place is offering vice presidency to the person who's in first place." Obama said the nomination process would have to be a choice between himself and Clinton, saying "I don't want anybody here thinking that 'Somehow, maybe I can get both, by nominating Clinton and assuming he would be her running mate. Some suggested that it was a ploy by the Clinton campaign to denigrate Obama as less qualified for the presidency. Later, when Obama became the presumptive Democratic presidential nominee, former president Jimmy Carter cautioned against Clinton being picked as the vice presidential nominee on the ticket, saying "I think it would be the worst mistake that could be made. That would just accumulate the negative aspects of both candidates", citing opinion polls showing 50% of US voters with a negative view of Hillary Clinton. Selection criteria Though the vice president does not need to have any political experience, most major-party vice presidential nominees are current or former United States senators or representatives, with the occasional nominee being a current or former governor, a high-ranking former military officer (active military officers being prohibited under US law from holding political office), or a holder of a major position within the Executive branch. In addition, the vice presidential nominee has always been