A new Rasmussen poll knocks the props out from the main argument why conservatives who would prefer to be represented in the Senate by Marco Rubio should nonetheless support Charlie Crist. Crist, his supporters say, has two things going for him: he’s going to win the nomination anyway, and if nominated he’d do better in the general election. Certainly nobody would try to convince Republicans with a straight face that Crist would be a better Senator, given his support for the stimulus bill and other Obama initiatives.

Well, there’s been a bunch of polls showing Rubio gaining ground on Crist in the nomination fight, but now Rasmussen reports that Rubio would be a stronger general election candidate, as a new poll shows he would beat the leading Democrat in the race, Congressman Kendrick Meek, by 15 points:

A new Rasmussen Reports survey of Florida voters shows Governor Charlie Crist leading Representative Kendrick Meek by a 46% to 34% margin. In August, Crist led by 19 and in June he was ahead by 21.

Former Florida House Speaker Marco Rubio leads Meek by a similar margin, 46% to 31%. In August, Rubio led by 13 percentage points.

Note two things. Number one, while Crist also beats Meek, both men would win handily if the election was held today. That makes the “electability” argument a weak one. Florida is not an overwhelmingly Republican state, but it’s still congenial turf for a conservative, and Meek is a liberal Democrat out of step with the kind of moderates who might look like an otherwise difficult sell for Rubio. Rasmussen notes that Obama’s approval rating in the state is 42%, so a pro-Obama Republican isn’t being pro-Obama out of any necessity.

Second, the trend – Rubio is growing stronger against Meek, while Crist weakens, a trend consistent with their matchup in the primary, as well as with the fact that Rasmussen shows a 10-point drop (from 59% to 49%) in Crist’s approval rating as Governor.

And remember: all this is more than a year from Election Day, while Rubio is still lightly funded (his campaign only recently started coming into good fundraising numbers) and relatively lesser known. As Rasmussen notes, the state’s voters still haven’t developed especially hardened opinions yet as to any of the candidates:

Seventeen percent (17%) of Florida voters have a very favorable opinion of Crist, while 13% view him very unfavorably.

Meek, a fourth-term African-American congressman from a district on Florida’s East coast, is viewed very favorably by 10% and very unfavorably by 12%.

Thirteen percent (13%) see Rubio very favorably, but nine percent (9%) have a very unfavorable opinion of the Cuban-American legislator from Miami.

The Crist campaign is all about a balancing act between two disparate narratives: an air of inevitability in the primary and sufficient desperation about electability in the general to get Republicans to turn away from voting for the better man. Neither of those arguments looks good right now. Sorry, Charlie.