$(declare -p) keeps adding backslashes

From help declare:

-p        display the attributes and value of each NAME

Just running declare -p works as expected. So does running it in a subshell with (declare -p).

However, when using echo "$(declare -p)", i.e. executing the command in a subshell, catching stdout and echoing that to stdout again, I noticed something weird happening: With each call, the output of declare -p gets longer and additional backslashes appear. The execution also takes increasingly longer.

Output of first run of echo "$(declare -p)":

...
declare -x SHELL="/bin/bash"
...

Second run:

...
declare -x SHELL="/bin/bash"
...
declare -x SHELL=\"/bin/bash\"
...

Third run:

...
declare -x SHELL="/bin/bash"
...
declare -x SHELL=\"/bin/bash\"
...
declare -x SHELL=\\\"/bin/bash\\\"
...

What's going on here?