In a sign of the rapidly changing dynamics between Congress and the White House, Senate Minority Leader Mitch McConnell (R-Ky.) — President Barack Obama’s biggest obstacle to clearing his agenda over the past two years — will be standing alongside the president when he signs the $858 billion tax cut bill Friday.

McConnell’s appearance at the 3:50 p.m. event marks the first time he will be attending a bill signing since Obama took office. Also telling is that none of House Democratic leadership will be at the event and only one Senate Democratic leader, Majority Whip Dick Durbin (Ill.), will attend.

After days of Democratic intraparty scuffling, the House voted late Thursday to pass the measure Obama negotiated with Senate Republicans; the Senate easily passed the bill Wednesday. The package extends all Bush-era tax cuts for two years, extends unemployment benefits for 13 months, imposes a payroll tax holiday and scales back a scheduled increase on estate taxes.

The president infuriated his liberal flank by conceding to GOP demands that the bill include tax cuts for the wealthy, an issue that he railed against during his 2008 campaign. But a senior Democratic aide said Obama’s overtures to Republicans are a strategic move that will benefit his re-election bid in 2012.

“For now, the White House likes having the base mad at him; it shows independents he is not the socialist the right portrays him to be,” the aide said. “I think they are happy with how this all played out.”

In addition to McConnell and Durbin, nearly two-dozen lawmakers from both parties will attend the bill signing. They include Sens. Max Baucus (D-Mont.), Kent Conrad (D-N.D.) and Blanche Lincoln (D-Ark.), and Reps. Jason Altmire (D-Pa.), Shelley Berkley (D-Nev.), Sanford Bishop (D-Ga.), Charles Boustany (R-La.), Dave Camp (R-Mich.), André Carson, (D-Ind.), Susan Davis (D-Calif.), Danny Davis (D-Ill.), Jane Harman (D-Calif.), Jim Himes (D-Conn.), Tim Murphy (R-Pa.), Bill Pascrell (D-N.J.), Gary Peters (D-Mich.), Dave Reichert (R-Wash.), Mike Ross (D-Ark.), Steven Rothman (D-N.J.), Allyson Schwartz (D-Pa.), John Spratt (D-S.C.) and Debbie Wasserman Schultz (D-Fla.).