Between World War II and the turn of the 21st century, the Democratic Party only controlled the upper house for one year.

[12] Democrats won 32 of 62 seats in New York's upper chamber in the 2008 general election on November 4, capturing the Senate majority for the first time in more than four decades.

[58] The self-named "Gang of Four" refused to back Malcolm Smith (Queens) as the chamber's majority leader and sought concessions.

[59] Monserrate soon rejoined the caucus after reaching an agreement with Smith that reportedly included the chairmanship of the Consumer Affairs Committee.

[60] The remaining "Gang of Three" reached an initial compromise in early December that collapsed within a week,[61] but was ultimately resolved[62] with Smith becoming majority leader.

The move came after Republican whip Tom Libous introduced a surprise resolution to vacate the chair and replace Smith as temporary president and majority leader.

[68] According to The New York Times, Espada's power play "threw the Senate into turmoil and hobbled the state government, making the body a national laughingstock as the feuding factions shouted and gaveled over each other in simultaneous legislative sessions.

[72] Espada was defeated in a September 2010 primary election[73] in which the Democratic Party backed his challenger, Gustavo Rivera.

[84] In March 2011, "Gang of Four" member Senator Carl Kruger surrendered to bribery charges.

[89] Months prior to the passage of the redistricting legislation, the New York Daily News reported that according to Republican sources, adding a 63rd seat "to the current 62-member body would...make political coups like the one that shut down the chamber two years ago more difficult".

Democrats gained seats in Senate Districts 17 (where Democrat Simcha Felder defeated Republican incumbent David Storobin), 41, and 55 (where Ted O'Brien defeated Sean Hanna to win the seat vacated by the retiring Republican Sen. Jim Alesi), and won the election in the newly created Senate District 46 (discussed below).

[95] On December 4, 2012, it was announced that Senate Republicans had reached a power-sharing deal with the four-member Independent Democratic Conference (IDC).

Under their power-sharing arrangement, the IDC and the Senate Republicans to "jointly decide what bills [would] reach the Senate floor each day of the session", would "dole out committee assignments", would "have the power to make appointments to state and local boards", and would "share negotiations over the state budget".

Klein and Skelos also agreed that the title of Senate President would shift back and forth between the two of them every two weeks.

[109] Malcolm Smith was expelled from the IDC in April 2013 due to a scandal in which he attempted to bribe the Republican Party chairs in New York City for a Wilson Pakula to run in the upcoming New York City mayoral election.

[111][112] Sampson later forfeited his Senate seat after being convicted of making false statements to federal agents in relation to the initial embezzlement case.

[104][117][118] After the election, the IDC reversed course and continued its alliance with the Republicans in the 2015 legislative session[117][119] despite their conference's diminished role.

[121] After Skelos was convicted in December 2015, his seat was declared vacant, with a special election to be held on the presidential primary of 2016.

On Long Island, freshman Sen. Michael Venditto was defeated in a close race by Democrat John Brooks.

[129] In Buffalo, the open seat vacated by Democratic Sen. Mark Panepinto (who did not seek re-election) was won by Republican Erie County Clerk Chris Jacobs.

[130] Newly elected Democratic Sen. Marisol Alcantara also announced that she would join the IDC, after Klein assisted her campaign.

[131][132] Liberal groups in New York State, including the Working Families Party, called on Gov.

[143] Stewart-Cousins was formally elected Majority Leader and Temporary President on January 9, becoming the first woman to hold the post.

[148][149] On July 20, 2020, Sen. Chris Jacobs stepped down after being elected to the United States House of Representatives.

[10] Sen. Tim Kennedy ran for the U.S. House of Representatives in 2024[150] and prevailed; he left the Senate and became a member of Congress.