Ace polling analysts Mark Blumenthal and Adam Carlson have an update on the battle for control of the U.S. Senate, and Republicans aren’t going to like it. Writing at HuffPo, Blumenthal and Carlson explain:

…With the exception of Connecticut, where a new poll released on Thursday indicates a very close race for the open Senate seat being vacated by independent Sen. Joe Lieberman, Republicans have seen few positive trends in their uphill battle to regain control of the U.S. Senate.
Currently, a combination of both returning senators and also candidates leading in 2012 contests would give the Democrats 48 seats, with 51 needed for a majority. One independent candidate likely to caucus with the Democrats continues to lead in polls in Maine. To retain control of the Senate, the Democrats would need to carry just two of eight races now considered toss-ups, a list that has been expanding in recent weeks.

The authors review competitive Senate races, now trending Democratic and conclude:

…In recent weeks, the Republican candidates appear to have lost ground in Senate races in Arizona, Indiana, Wisconsin and Missouri, while gaining only in Connecticut. With less than five weeks remaining before the votes are counted, the odds of a Republican Senate majority appear long.

That’s quite a change from a year ago, when a GOP takeover of the Senate was considered all but a done deal.