Can the president send troops to polling places?

Under 18 U.S.C. 592, a federal officer who orders or brings troops to a polling place commits a crime. The only exception is to repel armed enemies of the United States. The penalty is a fine, up to five years in prison, or both, and the person shall be disqualified from holding any office of honor, profit, or trust under the United States.

Separately, the Posse Comitatus Act, 18 U.S.C. 1385, makes it a crime to willfully use the armed forces to execute the laws except where the Constitution or an Act of Congress expressly allows it. The penalty is up to two years.

Under 10 U.S.C. 251, troops may be sent to suppress an insurrection against a state government only at the request of the state's legislature, or its governor if the legislature cannot be convened. Acting without a request under 10 U.S.C. 253 is limited to obstruction of federal law or rights that state authorities are unable, fail, or refuse to protect. 10 U.S.C. 254 first requires a proclamation ordering insurgents to disperse.

Intimidating a voter in a federal election is also a crime under 18 U.S.C. 594.