Vote for me to stop Donald Trump. That is Sen. Marco Rubio's message to Florida voters this week as the Republican establishment desperately tries to prevent the billionaire from winning the Republican nomination for president and completing a hostile takeover of the party. It's a weak argument from a weak candidate who is not prepared to be president.Throughout his political career, Rubio has focused on promoting himself and preparing for his next move rather than providing leadership to effectively address the challenges of the moment. Relying on a charming personality and a smooth speaking style, he has been more talk than action, more gimmick than substance, more opportunist than committed public servant. The result is a thin resume, a reputation for failing to pay attention to detail and a tendency to bend when the political winds shift.Let's remember that as the second-youngest speaker of the Florida House, Rubio's big gimmick was a blank book that he filled with 100 ideas that ranged from education reforms to promoting alternative energy. Yet during his speakership between 2006 and 2008, less than a quarter of those ideas became law. He gave up on his boldest idea, a regressive proposal to eliminate property taxes on primary homes in exchange for a gradual 2.5-cent sales tax increase, when the Senate wisely refused to go along.Let's remember the other highlights of Rubio's time in Tallahassee. It was while he was House speaker that Rep. Ray Sansom inserted $6 million into the state budget for a community college building that was really an airport hangar sought by a friend. It was Rubio who made it a priority for his friends on the state appellate court to get the $48 million "Taj Mahal" courthouse in Tallahassee. It was Rubio who charged thousands of dollars to his Republican Party credit card for personal expenses such as repairs to the family minivan that he says he repaid. So much for the fiscal responsibility Rubio likes to preach.Let's remember that Rubio's single term in the U.S. Senate has been devoid of a single significant accomplishment, unless we count a successful sneak attack on a small portion of the Affordable Care Act. He rose to national prominence as a key member of a bipartisan group of senators who passed sweeping immigration reform. True to form, Rubio abandoned it when the heat was turned up by opponents, and he has spent much of this campaign trying to explain himself without satisfying anyone.Rubio is a leader in Washington in one respect: He has missed more votes than any other senator in the past 12 months. To be fair, that is only slightly worse than Barack Obama's Senate voting record for the same period in the run-up to the 2008 election, PolitiFact reports. But the fact-checkers also show that Rubio's voting record is worse than Obama's in nine of the 12 previous quarters before the presidential election. The best argument for a promotion is a stellar performance in the current job, and Rubio fails that test.One of this year's ironies is that the antiestablishment Republican voters whom Rubio relied upon to win the U.S. Senate race in 2010 have abandoned him. The 2016 version of the tea party wave is angrier, more disillusioned and wider. Rubio, who has spent his career plotting his next move and exploiting opportunities rather than building a strong record and a natural constituency, has no viable way forward absent a Florida miracle. He also has damaged his personal brand with robotic debate performances and foolish attempts to match Trump's crudeness.Even Rubio's argument that Florida Republicans should vote for him Tuesday as the best way to stop Trump rings hollow. Sen. Ted Cruz of Texas has more convention delegates than Rubio. Gov. John Kasich of Ohio has broader appeal and a better shot of winning his home state. A vote for Rubio may be a protest vote — but it won't be a vote for someone who is prepared to be president.