The Dow Jones industrial average added 39.50 points to close at 6,081.18. At midday, the barometer of big U.S. companies was up almost 52 points, nearing a record for the first time in two weeks.
Advancers outnumbered decliners by more than a 3-to-2 margin on the New York Stock Exchange, with 1,488 up, 956 down and 829 unchanged.
NYSE volume totaled 486.05 million shares, vs. 391.09 million in yesterday.
The S&P 500 rose 7.41 to 714.14, leaping past Oct. 18's record finish at 710.82. The NYSE's composite index rose 3.36 to 378.43, narrowly beating its previous high at 378.32, also set Oct. 18.
The Nasdaq composite index rose 8.58 to 1,229.06, and the American Stock Exchange index rose 1.86 to 573.62.
Analysts said investors have shrugged off recent worries the Democrats might firm their grasp on the federal government by winning majorities in the Senate and House of Representatives.
The notion of a freer legislative hand and fewer obstacles to new government spending had been viewed as an inflationary threat.
Bonds rallied early today.
As bond prices rose, the yield on the 30-year Treasury bond - a key determinant of corporate and consumer borrowing costs - fell to 6.59 percent, down from late Monday's 6.66 percent and the lowest finish since April 2.