His popular prestige got a big boost in 2008, when the Senate was voting on a controversial and contentious law to increase taxes on grain exports. The voting ended in a tie, which gave Cobos, as President of the Senate, the deciding vote. In a stunning and now notorious move, he voted against the law. This led to strong criticism from his party, who deemed him a traitor, and approval from sectors of the population that opposed the government. As he further distanced himself from the FPV, the UCR revoked his expulsion from the party. By 2010, he was considered a potential candidate for the 2011 presidential elections.