What type of voters do campaigns generally spend the most time targeting? the base voters if a party voters registered for opposing parties independent and undecided voters voters registered for minor parties

 Independent and undecided voters.

Explanation:

The major political parties each depend on their "base" -- those who consistently vote Democrat or Republican.  They'll engage in efforts to make sure their base voters get out to the polls in large numbers.   But because the base of voters for either party is not sufficient to gain an overall majority of the voting public, the independent and undecided voters are the main targets for each party's campaign efforts and advertising.  To win an election, a party needs not only its base but also needs to win more of the independent/undecided voters than the other party does.

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