You have it exactly backwards, in my opinion. Congress votes for legislation and the budget - you need conservatives in Congress if anything is to be accomplished. If Congress were conservative, it wouldn't matter so much who the president was; he wouldn't get the intrusive social programs and other big government legislation.
Also, if people were electing true conservatives to lower positions, it would send a message to those at higher levels.
Remember your congresscritters represent you personally, so you should truly want a true conservative in that position.
The president represents the entire country - and the entire country isn't conservative, so it's harder to get a conservative president. Worth hoping for, but not likely to happen until there's a change country-wide and at lower levels.