Of course, the downside is you must build it yourself...
\documentclass{article}
\usepackage{fixltx2e}
\usepackage{tabstackengine}
\stackMath\TABbinary
\newsavebox\tempbox
\newlength\templen
\def\rl#1{%
\sbox\tempbox{$#1$}%
\setlength\templen{\wd\tempbox}%
\llap{\rule{1.5pt}{.1ex}}\rule{\templen}{.1ex}\rlap{\rule{1.5pt}{.1ex}}}
\setstacktabulargap{0pt}
\begin{document}
\tabularShortstack{crcrcrcrcl}{
&x^4&-&3x^3&+&x^2 &+&3x&-&2 = (x-1)(x^3 - 2x^2 -x +2)\\
-&x^4&+&x^3 & & & & & &\\
\rl{-}&\rl{x^4}&\rl{-}&\rl{3x^3}&&&&&&\\
& &-&2x^3&+&x^2 &+&3x&-&2\\
& & &2x^3&-&2x^2& & & &\\
&&&\rl{2x^3}&\rl{-}&\rl{2x^2}&&&&\\
& & & &-&x^2 &+&3x&-&2\\
& & & & &x^2 &-& x& &\\
&&&&&\rl{x^2}&\rl{-}&\rl{3x}&&\\
& & & & & & &2x&-&2\\
& & & & & &-&2x&+&2\\
&&&&&&\rl{-}&\rl{2x}&\rl{+}&\rl{2}\\
& & & & & & & & &0
}
\end{document}

If you really wanted to extend the horizontal lines...
\documentclass{article}
\usepackage{fixltx2e}
\usepackage{tabstackengine}
\stackMath\TABbinary
\newsavebox\tempbox
\newlength\templen
\def\rl#1{%
\sbox\tempbox{$#1$}%
\setlength\templen{\wd\tempbox}%
\llap{\rule{1.5pt}{.1ex}}\rule{\templen}{.1ex}\rlap{\rule{1.5pt}{.1ex}}}
\setstacktabulargap{0pt}
\begin{document}
\tabularShortstack{crcrcrcrcrl}{
&x^4&-&3x^3&+&x^2 &+&3x&-&2& = (x-1)(x^3 - 2x^2 -x +2)\\
-&x^4&+&x^3 & & & & & & &\\
\rl{-}&\rl{x^4}&\rl{-}&\rl{3x^3}&\rl{+}&\rl{2x^2}&\rl{+}&\rl{3x}&\rl{-}&\rl{2}&\\
& &-&2x^3&+&x^2 &+&3x&-&2&\\
& & &2x^3&-&2x^2& & & & &\\
&&&\rl{2x^3}&\rl{-}&\rl{2x^2}&\rl{+}&\rl{3x}&\rl{-}&\rl{2}&\\
& & & &-&x^2 &+&3x&-&2&\\
& & & & &x^2 &-& x& & &\\
&&&&&\rl{x^2}&\rl{-}&\rl{3x}&\rl{-}&\rl{2}&\\
& & & & & & &2x&-&2&\\
& & & & & &-&2x&+&2&\\
&&&&&&\rl{-}&\rl{2x}&\rl{+}&\rl{2}&\\
& & & & & & & & &0&
}
\end{document}

polynompackage. Have you attempted to contact the package's maintainer(s) to ask if such a feature might be provided? – Mico Oct 26 '14 at 18:27polynom. But yes, asking the maintainer may be the right thing to do. – Gaussler Oct 26 '14 at 18:38