Ronald Reagan has emerged as the candidate most likely to win the 1980 presidential election, according to a new ABC News-Harris Survey.

One reason for his current preeminence is the continuing troubles encountered by President Carter. But equally important is the fact that Reagan has become a respected figure on the political scene.

The American electorate has become increasingly favorable to the Reagan candidacy:

By 52 to 47 percent, a majority of the voters denies the proposition that "if elected president, Reagan will be nearly 70 years of age when he takes office, and that is too old considering how hard it is to do that job." Last October, a substantial 61-to-36 percent majority agreed with the statement.

By 53 to 42 percent, according to the survey of 1,188 likely voters nationwide, a majority feels that Reagan "has the personality and leadership qualities a president should have." This is a key measure of candidate acceptability.

By 69 to 26 percent, a sizable majority agrees that Reagan is "right to want to get government out of business so that free enterprise can operate freely."

At the same time, a 60 to 28 percent majority denies the charge that Reagan is "too close to big business to be president." A much narrower 47 to 37 percent plurality objected to this criticism last October.

By 56 to 40 percent, a majority feels that Reagan has "a highly attractive personality and would inspire confidence as president," up from 53 to 39 percent who shared that view last October.

However, Reagan still has a couple of real vulnerabilities:

By far the most serious negative is the 68 to 27 percent majority of voters who told the ABC News-Harris Survey that "he seems to make too many off-the-cuff remarks which he then has trouble explaining or has to apologize for making."

By 46 to 43 percent, a plurality of the voters agrees with the claim that "Reagan is not right when he claims that federal income taxes could be cut 30 percent without causing a budget deficit, which would be inflationary." During his campaigning, Reagan generally has said he looks with favor upon the provisions of the Kemp-Roth bill, which would cut the federal tax rate 30 percent, but not cut federal spending.