How do I animate two letters swapping?

I am trying to make a website where hovering over a misspelling consisting of transposition of two letters corrects it, like so:

var swap = document.querySelector('.swap');

swap.addEventListener('mouseover', swapIn);
swap.addEventListener('mouseout', swapOut);

function swapIn(e) {
  e.target.parentNode.firstChild.classList.toggle('shifted-right');
  e.target.parentNode.lastChild.classList.toggle('shifted-left');
}

function swapOut(e) {
  e.target.parentNode.firstChild.classList.toggle('shifted-right');
  e.target.parentNode.lastChild.classList.toggle('shifted-left');
}
body {
  font-size: 24px;
}

.swap {
  display: inline;
}

span {
    -webkit-transition: all 0.3s linear;
    -moz-transition: all 0.3s linear;
    -o-transition: all 0.3s linear;
    transition: all 0.3s linear;
}

.shifted-right {
  margin-left: 20px;
  color: blue;
}

.shifted-left {
  margin-left: -25px;
  color: red;
}
E<div class="swap" id="swap"><span class="left-swap" id="ls">q</span><span class="right-swap" id="rs">c</span></div>uis me vivit fortunatior?

However, as you can see, the letters don’t swap well, and besides, I don’t want to calculate the precise margins for each different letter width.

What’s a better approach to doing this?