In the fight for control of the US Senate, the majority may come down to which factor carries more weight: the map or the environment.

Government shutdown all but guaranteed as House Speaker Mike Johnson, R-La., says earliest action on Senate-passed spending bill is Monday, with two-thirds majority potentially needed.

Senate Democrats are threatening to block legislation that would fund the Department of Homeland Security and several other agencies Thursday, potentially bringing the government a step closer to a partial shutdown if Republicans and the White House do not agree to new restrictions on President Donald Trump's surge of immigration enforcement.

Federal funding is set to lapse at midnight Friday, and votes are still required in both chambers of Congress.

The deal will fund most of the government through September and the Department of Homeland Security for two weeks

Sen. Thom Tillis, R-N.C., has separately vowed to hold up the nomination until the DOJ resolves its criminal investigation of Fed Chair Jerome Powell.

In Alaska, Ohio, North Carolina and Maine, Democrats have fielded Senate candidates who won statewide office before, raising expectations to flip seats.

Government shutdown looms as Senate battles over DHS funding package, with a test vote scheduled for Thursday.