Let the number of voters be $X$.
The number of valid votes = $X-68$
Votes secured by winning candidate is $52$% of valid votes = $0.52(X-68)$
Votes secured by losing candidates (remaining votes) = $0.48(X-68)$
It is given that the winner leads by 98 votes which give us the following relation:
$0.52(X-68)=0.48(X-68)+98$
Solving this, we get $X=2518$
Hence the total valid votes are $2518-68=2450$ and total votes polled = $2518$