MADISON, Wis. — U.S. Sen. Tammy Baldwin on Wednesday introduced legislation intended to prevent the president from sending U.S. Immigration and Customs Enforcement agents or National Guard troops to polling places in November. Baldwin’s office said the measure would block the use of federal immigration officers and National Guard personnel at polling locations. The proposal follows concerns raised in Dane County about the potential presence of federal agents at voting sites and the effect that could have on voters and election workers. The Dane County clerk criticized what she characterized as a lack of public response to threats involving federal agents at the polls. The concerns center on whether a visible federal presence could intimidate voters or interfere with the administration of elections. The legislation was introduced as Wisconsin prepares for the November election. The information released Wednesday did not include details about the bill’s sponsors, its path through Congress or whether federal officials have announced plans to deploy agents to Wisconsin polling places. Polling places are generally administered by state and local election officials, who are responsible for conducting voting and protecting access to the ballot. Any federal deployment near voting sites could raise questions about authority, voter intimidation and the independence of local election administration.