by Paul KaneFor the latest sign of the political resonance of the global warming issue, check out the list of cosponsors that Sens. Bernie Sanders (I-Vt.) and Barbara Boxer (D-Calif.) have lined up for their bill to combat greenhouse gasses.All four Senate Democrats seeking the 2008 presidential nomination are signed on as supporters. Three of the Democrats signed on within the last week to what Sanders and Boxer are promoting as "gold standard" legislation -- a plan to slash carbon dioxide emissions 80 percent from their 1990 levels by 2050.A quick search of the Library of Congress's Thomas site shows that the Democratic frontrunners Hillary Rodham Clinton (N.Y.) and Barack Obama (Ill.) signed on to support the bill on the exact same day -- last Thursday.Aides to Sanders and Boxer, who chairs the Environment and Public Works Committee, declined to say which frontrunner signed up first that day or whether it was an actual tie.If political points are awarded for quickest reaction to an issue that the liberal base is increasingly concerned about, then Sen. Christopher Dodd (D-Conn.) is the hands down winner of the '08 field. Dodd signed on with Sanders and Boxer two weeks after they officially unveiled their bill in mid-January.It took Clinton and Obama another three-and-a-half months to come aboard the Sanders-Boxer express, despite many months on the trail spent talking about the issue and months of hype surrounding former Vice President Al Gore's movie, "An Inconvenient Truth."Sen. Joseph Biden (D-Del.) joined a few more senators this week, bringing the total number of Senate Democrats supporting the bill to 17. That's a long way from 51 votes for a majority or the 60 votes they would need to overcome a likely filibuster from Republicans staunchly opposed to legislation largely derided by conservatives as anti-business.As Steven Mufson reported in today's Post, Obama has his own plan, which would cut carbon dioxide emissions by improving fuel efficiency in cars. (Nevermind, as Mufson noted, that some greens aren't happy with Obama's support for "coal-to-liquids technology.")Beyond the popularity of Gore's movie (and continued talk of a potential Gore campaign), global warming has become a major issue among the Democratic field. Even Republicans like Sen. John McCain (Ariz.) have embraced the issue.